enforce consistent API

[akaszynski]

Overview

In keeping with our goal to be consistent with numpy, this PR changes the behavior for several methods to return tuple rather than lists or numpy.ndarray. This includes:

• pyvista.DataSet.bounds list -> tuple
• pyvista.DataSet.extent list -> tuple
• pyvista.DataSet.cell_bounds list -> tuple
• pyvista.Grid.dimensions list -> tuple
• pyvista.UniformGrid.origin list -> tuple
• pyvista.UniformGrid.spacing list -> tuple
• pyvista.ExplicitStructuredGrid.spacing np.ndarray -> tuple
• pyvista.ExplicitStructuredGrid.visible_bounds list -> tuple

Why?

There's no reason for returning a list, which are more flexible than tuples and imply that there's a reason to append or manipulate the data. Rather, the immutability of the tuple implies that the data returned is "read only". And because VTK already returns tuples as the default datatype for GetBounds and other class methods, this actually simplifies our code. Plus, this matches numpy's shape, ndim and other properties.

Other Changes

• ExplicitStructuredGrid.hide_cells and show_cells now accepts sequences rather than just numpy.ndarray.
• Added type hints to several methods.
• Improved the documentation of grid.py in several places, including adding examples to the docstrings.
• Resolve UniformGrid with negative spacing results in wrong subset when using extract_subset #1967 by disallowing negative spacing.

[codecov]

Codecov Report

Merging #1971 (99cbd51) into main (e56db11) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1971      +/-   ##
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- Coverage   92.99%   92.99%   -0.01%     
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  Files          74       74              
  Lines       15484    15482       -2     
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- Hits        14400    14398       -2     
  Misses       1084     1084